Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$10.90	7.812%	$11.7515	$11.75	$11.75	$11.80
Purchase #2	$44.90	11.594%	$50.1057	$50.11	$50.10	$50.10
Purchase #3	$213.93	10.497%	$236.3862	$236.39	$236.40	$236.40
Purchase #4	$90.69	10.844%	$100.5244	$100.52	$100.50	$100.50
Purchase #5	$235.45	12.816%	$265.6253	$265.63	$265.65	$265.60
Purchase #6	$48.41	8.627%	$52.5863	$52.59	$52.60	$52.60
Purchase #7	$130.59	12.872%	$147.3995	$147.40	$147.40	$147.40
7 purchase totals =	$774.87		$864.3789	$864.39	$864.40	$864.40